Sunscreen: What you need to know

Sunscreen is one of the most powerful tools you can use to protect your skin’s health—both now and in the long run. Daily sun exposure without protection is responsible for up to 90% of premature skin aging, including fine lines, wrinkles, pigmentation, and loss of elasticity. Even just 10-minutes of unprotected sun time can trigger DNA damage at the cellular level, increasing your risk of sunburns, inflammation, and skin cancer over time. Sun protection isn’t just about aesthetics—it’s about preserving your skin’s integrity, preventing long-term damage, and supporting healthy skin aging. 

But with so many options available, understanding the differences between physical and chemical sunscreens—and what truly works—can be overwhelming. Here’s everything you need to know to make the best choice for your skin and health.

What the SPF: What is SPF and Why Is It Important?

SPF measures sunscreen protection from UVB rays, which cause sunburn and skin cancer. Higher SPF allows longer sun exposure without burning, but higher values offer diminishing returns.

• SPF 30 blocks 97% of UVB rays
• SPF 50 blocks 98% of UVB rays
• SPF 100 blocks 99% of UVB rays

This means that SPF 50 does not provide twice the protection of SPF 25, and SPF 100 only provides a marginal increase in UVB protection. The key takeaway is that SPF 30 to 50 is sufficient for most people, and higher SPFs can give a false sense of security, leading to inadequate reapplication.

Why SPF Alone is Not Enough

SPF only measures UVB protection, but UVA rays penetrate deeper into the skin, contributing to premature aging and increasing skin cancer risk. A sunscreen labeled “broad-spectrum” protects against both UVA and UVB rays and is essential for full sun protection. Additionally, sunscreen effectiveness depends on proper application and reapplication:

Tips for better Protection

• Apply at least 1 ounce (about a shot glass worth) for full-body coverage.
• Reapply every 2 hours, especially after swimming or sweating.
• No sunscreen is truly waterproof—look for “water-resistant” formulas that last 40–80 minutes in water.

Physical vs. Chemical Sunscreens

Physical Sunscreens

Physical sunscreens (also known as mineral sunscreens) create a physical barrier that reflects UVA and UVB rays away from the skin. They contain active ingredients like zinc oxide and titanium dioxide, which are not absorbed into the skin but rather sit on top as an extra protective layer. Nano-particle technology has been developed to make zinc oxide and titanium dioxide particles smaller, which helps to improve their application and reduce the classic white cast without compromising the UV protection.

Pros

• Broad-spectrum protection against UVA and UVB rays
• Less likely to cause irritation for sensitive skin
• Better for acne-prone (non-comedogenic)

Cons

• Can leave a white cast on the skin, although newer mineral sunscreen options utilize nano or invisible zinc technology to help reduce the white cast even further. 

Chemical Sunscreens

Chemical sunscreens absorb UV radiation, converting it into heat that disperses over the skin. These sunscreens use a variety of chemicals that act like sponges, soaking up the suns UV radiation before it penetrates the deeper layers of the skin. Some chemical sunscreen ingredients have raised safety concerns, such as their potential endocrine-disrupting effects and environmental impact.

Pros

• Lightweight, blends easily into the skin
• No white cast

Cons

• Some ingredients may be absorbed into the skin
• More likely to clog pores and be comedogenic
• Can be more irritating for people with sensitive skin 

What are EDCs: Endocrine-Disrupting Chemicals 

Some chemical sunscreen ingredients have raised concerns about potential hormone disruption based on animal studies. While human studies are less conclusive, it is reasonable to be cautious given the widespread exposure to endocrine disruptors. To minimize exposure, choose a mineral sunscreen vs chemical sunscreens that are more likely to contain ingredients that can be more disruptive to your health and have potential environmental harms. 

Ingredients to Avoid in Sunscreens:

• Oxybenzone – A known endocrine disruptor that can interfere with hormone function and has been linked to coral reef bleaching.
• Octinoxate – Another hormone-disrupting chemical that can accumulate in the body and harm marine ecosystems.
• Homosalate – Can disrupt estrogen, androgen, and progesterone levels when absorbed into the body.
• Octocrylene – Can break down into benzophenone, a potential carcinogen and skin allergen.
• Parabens (e.g., methylparaben, propylparaben) – Preservatives that may contribute to hormone disruption.
• Retinyl Palmitate (Vitamin A derivative) – Can increase skin sensitivity to the sun and may be linked to an increased risk of skin tumors.
• Aerosol Spray Sunscreens – Can contain carcinogenic contaminants and pose inhalation risks.

Sun Exposure and Skin Cancer Risk

The age at which you get your first sunburn is a predictor of future skin cancer risk. There is no safe level of unprotected sun exposure due to the increasing strength of UV rays, changes in the ozone layer, and rising global radiation levels. People who spend time outdoors for work (e.g., construction workers, landscape workers etc) without the intent to tan do not have a significantly elevated risk. However, those who tan purposely are at a much higher risk of skin cancer.

Common Sunscreen Myths

Sunscreen inhibits vitamin D production:

    A common concern is that sunscreen blocks vitamin D synthesis. However, evidence does not strongly support this claim. Studies show that regular sunscreen users do not have significantly lower vitamin D levels, likely because perfect application is unrealistic. Photosynthesis of vitamin D varies person to person, making supplementation a safer choice.

Homemade sunscreens are a safer option: 

    I love a good DIY, but not when it comes to my sunscreen, its a NO. While some of these may have minor UV-blocking properties, they do not provide reliable broad-spectrum protection against both UVA (skin aging, DNA damage) and UVB (sunburn, skin cancer) rays. Some natural skincare enthusiasts promote homemade sunscreens using ingredients like raspberry seed oil, carrot seed oil, almond oil, coconut oil, shea butter plus zinc oxide powder. The fact is, these do not provide reliable sun protection and can actually increase the risk of burns. 

• Studies show that coconut oil, for example, has an SPF of around 1–8, which is far below the recommended SPF 30 for effective protection.
• Non-nano zinc oxide (the safest sunscreen ingredient) needs to be properly formulated and evenly dispersed in a product to be effective—something that’s nearly impossible to achieve in a homemade mixture.
• Home made sunscreen have no standardized SPF testing: commercial sunscreens undergo rigorous testing to determine their SPF rating and UVA/UVB coverage. Homemade sunscreens have no way of verifying their actual sun protection factor, meaning the protection level is unpredictable.
• Uneven application & coverage: professional sunscreens use stabilizers and emulsifiers to ensure even distribution of active ingredients. In homemade versions, clumping and separation are very common, leading to patchy protection and increasing the risk of sunburn and skin damage.
• Lack of photo-stability: Most commercial sunscreens contain stabilizers to prevent breakdown in sunlight. Homemade versions do not, meaning any protection they offer could degrade quickly with UV exposure.
• Increased risk of skin cancer & premature aging: using ineffective sun protection increases the risk of cumulative sun damage, which is the leading cause of wrinkles, hyperpigmentation, and skin cancer (including melanoma!).

You don’t need sunscreen on cloudy or cold days: 

    Up to 80% of UV rays can actually penetrate through clouds. This means your skin is still exposed to potential damage even if the sun is hidden behind a rain or snow (talking to you Canadians) cloud —  in fact, snow, sand, and water can also reflect UV rays, increasing your exposure and risk of burning.

Chemical sunscreens are toxic and get absorbed into the bloodstream:

    Some studies have detected certain chemical sunscreen ingredients in the bloodstream, particularly in animal studies, while human research in this area is still evolving. However, current evidence does not indicate that these levels are harmful when used as directed. Ongoing research continues to explore the potential endocrine-disrupting effects of some chemical sunscreens, but at present, regulatory bodies such as Health Canada and the FDA consider them safe for use. If a chemical sunscreen is your only option, it is far better to wear it than to go unprotected. However, if you have the choice, mineral sunscreens containing zinc oxide or titanium dioxide offer an excellent alternative, as they provide broad-spectrum protection while sitting on the skin’s surface rather than being absorbed.

References: 

• American Academy of Dermatology. (2023). "Sunscreen FAQs." Retrieved from www.aad.org
• Environmental Working Group. (2023). "Sunscreen Guide." Retrieved from www.ewg.org
• The Skin Cancer Foundation. (2023). "The Truth About Sunscreen and Vitamin D." Retrieved from www.skincancer.org
• National Library of Medicine. (2022). "Endocrine Disrupting Chemicals in Sunscreens." Retrieved from www.ncbi.nlm.nih.gov
• Wang, S. Q., et al. (2019). "SPF and UVA Protection: A Review of Current Sunscreen Standards." Journal of the American Academy of Dermatology.
• Matta, M. K., et al. (2020). "Effect of Sunscreen Application Under Maximal Use Conditions on Plasma Concentration of Sunscreen Active Ingredients: A Randomized Clinical Trial." JAMA.
• Krutmann, J., & Schalka, S. (2021). "UVA-Induced Skin Aging and Protection with Sunscreens: From Theory to Practice." Photodermatology, Photoimmunology & Photomedicine.
• Downs, C. A., et al. (2016). "Toxicopathological Effects of the Sunscreen UV Filter Oxybenzone in Coral Reefs." Archives of Environmental Contamination and Toxicology.
• Darvin, M. E., et al. (2017). "Influence of Sunscreens on the Skin Barrier Function." Skin Pharmacology and Physiology.